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Posted: August 3, 2009

Smallest electric motor runs on only two atoms

(Nanowerk News) The principle is easy: one starter and one motor atom in a ring of laser light - and a bit of fine tuning, in order to move always into the right direction.

The research group of the theoretical physicist Prof. Peter Hänggi from the University of Augsburg has invented a concept for the minimal version of an electric motor, which gets on with only two atoms. The study has recently been published in the renowned scientific journal Physical Review Letter ("ac-Driven Atomic Quantum Motor").

An ordinary electric motor is based on the principle that mechanical work is done by electrical energy. Hänggi and his co-authors Dr. Alexey Ponomarev and Dr. Sergey Denisov now have transferred this principle into the nano world, on the level of single atoms. „Since on that level the laws of classical physics are not applicable, but those of quantum mechanics, the conversion of electric energy into mechanical work is not a trivial challenge,” Hänggi stresses.

The three physicists have met this challenge. They designed a magnetically driven atomic quatum motor, by first “catching” two atoms in a ring of laser ligth - one motor and one starter atom. This construction becomes a motor, when motor and starter atom meet each other and interact via electro-magnetic forces. The starter atom gives the motor atom a “kick”. “Since there is no friction in this world, it is crucial to give the motor a moving direction when it has been kicked off, in order to enable it to perform work against an outer force”, explains Hänggi.

To keep the motor atom on its course, specifically tuned external electro-dynamic forces are needed. “This ‘Tuning’, which avoids a false turn-over of the motor atom in the ring, is the point”, emphasizes Hänggi. He has also a technical term for it: “breaking of symmetry”. Speaking of Tuning: What makes this smallest motor of the world superior to other motors: “After switching off the electro-magnetic drive, it simply runs further on, because there is no braking friction in its quantum world, which consists only of two atoms.”